The invention relates to a monitoring apparatus for a steam plant and a method of operating such an apparatus.
It is known to provide a steam plant for generating and distributing useful energy, in the form of steam, to the point-of-use in various industrial applications.
Excessive condensate, accumulated as a result of utilising the steam's latent energy in a process, is typically undesirable since it may act as a barrier to heat transfer and can also lead to damaging “water-hammer” and can cause corrosion of the pipelines. It is therefore required to drain the condensate as soon as it is formed. The condensate is typically drained from the lowest points of the main plant pipeline through one or more drain lines. In order to limit steam loss from the plant, each drain line is provided with a respective steam trap, which ideally operates to drain condensate whilst at the same time preventing the escape of live steam.
Whilst the presence of condensate in the main plant pipeline is typically undesirable, the hot condensate will nevertheless contain useful energy. Therefore, in a typical steam plant the drain lines and steam traps will form part of a larger condensate recovery system designed to drain condensate (but not live steam) from the main plant and to recycle the drained condensate through a steam boiler for subsequent use in the plant. Thus, each drain line will typically feed into a condensate return line that in turn feeds one or more down-stream receiver tanks. The receiver tanks act as temporary storage units for drained condensate, which is then typically pumped from the receiver tank into the feed-tank of a steam boiler as required.
The efficient operation of a steam plant and condensate recovery system relies upon effective operation of the steam traps, and therefore the checking and maintenance of steam traps is very important. Conventionally, a detailed manual maintenance survey of steam traps will be carried out to identify faulty steam traps, possibly as part of a larger system audit. Current practice is to carry out such steam trap surveys periodically. However, a steam trap survey is normally a rigorous, tedious and often time-consuming process. Consequently, surveys are usually only carried out at periodic intervals of six to twelve months. Thus, in a worst case scenario it might be twelve months or more before a faulty steam trap is properly diagnosed in a maintenance survey. Given the large number of traps associated with a steam plant, significant numbers of traps could in principle become faulty in the intervening period between maintenance surveys.
WO 2009/106851 discloses a condensate recovery system which uses the correlation between steam levels and acoustic levels in the condensate return line to monitor the operation of the steam traps. The condensate recovery system comprises an acoustic sensor which provides an output indicative of the collective steam loss through the steam traps of the steam plant. The output therefore provides an indication of the condition and operation of the steam traps and enables faults to be identified.
The invention seeks to optimise such monitoring techniques to provide more efficient operation.